While the CAPT installation procedure is indeed non-standard, this is the only way I have managed to successfully install a Canon LBP2900 via USB, and a Canon LBP6310dn via ethernet on both Arch Linux and Linux Mint on three separate computers. This prompted me to document the steps in the Wiki, after adapting them to Arch Linux from the original, linked, Ubuntu article.

Furthermore, adding a printer to CUPS using lpadmin is a perfectly valid method.

Did the person who questions the instructions even attempt to install a CAPT printer himself, before disputing the factual accuracy?

Canon's own installation instructions use this method, rather than a standard installation procedure using the CUPS web interface, although they don't work due to the port number being incorrect.

While CAPT printers are detected by, and can be added via the CUPS GUI, they do not work.